Too Sexy for Your Shirt?

Men everywhere want to know: What makes a man attractive to women? Poor dears – they’re so confused. Sometimes women seem attracted to responsible, stable, wealthy men, men who might make good fathers. But other times they seem drawn to the dangerous rogues, irresponsible and selfish, but oh so good-looking.

Psychological science is showing that what a woman finds sexy may in fact depend on when you ask her — and that there may be good evolutionary reasons for women’s varying tastes.

Steven W. Gangestad and his collaborators at the University of New Mexico have undertaken a series of studies mapping the sexual preferences of women across their monthly cycle. In the December issue of Current Directions in Psychological Science, Gangestad and coauthors Randy Thornhill (an evolutionary biologist) and Christine E. Garver-Apgar summarize a series of studies showing that during the few days women are ovulating — that is, when they are fertile — they display markedly increased preference for stereotypical sexiness traits: things like masculine facial features and voice, behaving competitively or arrogantly, and displaying talent (as opposed to wealth). At this time of the month, women’s preference for men other than their current partners also rises.

Gangestad and colleagues found that the attractiveness of traits that are supposed to make good life partners — things like kindness, intelligence, being a good father, or potential for wealth — are unchanged across the monthly cycle. And faithfulness actually diminishes as an attractive feature of males during the fertile days.

This pattern of shifting turn-ons actually makes sense, according to the researchers, if we think about sexiness as a sign of good genes.

Their reasoning goes something like this: Organisms tend to seek genetically fit reproductive partners in order to maximize their offspring’s chances of surviving and passing their genes on to subsequent generations. But in species like humans and many birds, in which both males and females contribute to raising offspring, biological suitability isn’t necessarily the same thing as being a caregiver. In many pair-bonding species, fidelity isn’t an absolute; and it sometimes happens that cuckolded fathers raise offspring that aren’t their own.

In this respect, humans actually have a lot in common with the collared flycatcher. Flycatchers form strong pair bonds, and males contribute their fair share to protecting and raising offspring. But despite this family-like structure, fertile female flycatchers sometimes seek sexual relations with other males when their partners aren’t looking. What’s more, their tastes in long-term partners (i.e., caregivers for their children) differ from their tastes in one-night-stands. During their extramarital flings, female flycatchers prefer males with big forehead patches. Such males are not very responsible or energetic when it comes to tending the nest or caring for offspring — they make poor longterm mates, in other words — but their patches signify top-notch genes.

In the human world, advertisements of good genetic health can be much subtler than a big forehead patch. One is physical symmetry — for example, evenness of finger length, wrist thickness, or ear size on both sides — and the researchers found that, when fertile, women don’t even have to see this quality to detect it (or at least, detect the genetic fitness it points to).

In one series of experiments, the researchers had men sleep in the same tee-shirt for two nights. Women then smelled the shirts in the laboratory and rated the shirts’ scents for attractiveness. When fertile — and only when fertile — women distinctly preferred the scents of men with strongly symmetrical facial and body features. Somehow (it is not known exactly how, although it probably involves substances derived from male hormones), they could smell the relative health of symmetrical men.

The researchers argue that women’s shifting attraction to different mates with different traits may be an echo of the forces of natural selection that shaped our species. It follows that men should show corresponding patterns of behavior, counterstrategies reflecting their own biological imperatives. Gangestad and his colleagues have shown that men are especially attracted to the scent of fertile women; and in a series of studies, they found that men tended to monopolize their partners’ time specifically during the fertile days.

For more on the “ovulatory shift hypothesis,” see “Adaptations to Ovulation: Implications for Human Sexual Behavior,” in the December 2005 issue of Current Directions in Psychological Science.